Souza Leonardo da Silva, Manzano Gonzalo, Fazio Rosario, Iemini Fernando
Instituto de Física, Universidade Federal Fluminense, 24210-346 Niterói, Brazil.
Departamento de Física, ICEx, Universidade Federal de Minas Gerais, Av. Pres. Antônio Carlos 6627, Belo Horizonte Minas Gerais 31270-901, Brazil.
Phys Rev E. 2022 Jul;106(1-1):014143. doi: 10.1103/PhysRevE.106.014143.
Recent predictions for quantum-mechanical enhancements in the operation of small heat engines have raised renewed interest in their study both from a fundamental perspective and in view of applications. One essential question is whether collective effects may help to carry enhancements over larger scales, when increasing the number of systems composing the working substance of the engine. Such enhancements may consider not only power and efficiency, that is, its performance, but, additionally, its constancy, that is, the stability of the engine with respect to unavoidable environmental fluctuations. We explore this issue by introducing a many-body quantum heat engine model composed by spin pairs working in continuous operation. We study how power, efficiency, and constancy scale with the number of spins composing the engine and introduce a well-defined macroscopic limit where analytical expressions are obtained. Our results predict power enhancements, in both finite-size and macroscopic cases, for a broad range of system parameters and temperatures, without compromising the engine efficiency, accompanied by coherence-enhanced constancy for finite sizes. We discuss these quantities in connection to thermodynamic uncertainty relations.
近期对小型热机运行中量子力学增强效应的预测，从基础研究角度以及应用角度都重新激发了人们对其研究的兴趣。一个关键问题是，当增加构成发动机工作物质的系统数量时，集体效应是否有助于在更大尺度上实现增强效应。这种增强效应不仅可以考虑功率和效率，即其性能，还可以考虑其稳定性，即发动机相对于不可避免的环境波动的稳定性。我们通过引入一个由连续运行的自旋对组成的多体量子热机模型来探讨这个问题。我们研究功率、效率和稳定性如何随构成发动机的自旋数量变化，并引入一个定义明确的宏观极限，在这个极限下可以得到解析表达式。我们的结果预测，在有限尺寸和宏观情况下，对于广泛的系统参数和温度范围，功率都会增强，且不影响发动机效率，同时有限尺寸下稳定性会因相干性增强。我们结合热力学不确定性关系讨论这些量。
